Workholder for abrasive machines



July 21., 1970 s. WINDEFORS 3,521,410

WORKHOLDER FOR ABRASIVE MACHINES Filed April 5, 1967 3 Sheets-Sheet 3 July 21, 1970 s. WINDEFORS 3,521,410

WORKHOLDER FOR ABRASIVE MACHINES Filed April 5, 1967 3 Sheets-Sheet 3 i on United States Patent 3,521,410 WORKHOLDER FOR ABRASIVE MACHINES Stig Windefors, Faktorigatan 35, Huskvarna, Sweden Filed Apr. 3, 1967, Ser. No. 627,780 Claims priority, application Sweden, Apr. 7, 1966, 4,836/66 Int. Cl. B24b 21/16 U.S. Cl. 51144 Claims ABSTRACT OF THE DISCLOSURE A device for carrying the workpiece in an abrading machine having a movable belt, against which the workpiece is pressed, comprising a pendulum, which is rotatable on a first axis and pivotable on a second axis, substantial y perpendicular to said first axis, and a workpiece holder, which is located at the free end of said pendulum and preferably rotatable on a horizontal axis, which is perpendicular to said axis of rotation. The invention also encompasses an abrasive belt provided with a coating of an abrasive composition which contains a plurality of layers of abrasive grains.

This invention primarily relates to grinding and polishing machines. In certain machines of this kind, e.g. for the emerying or polishing of workpieces having a comparatively complicated shape, the workpiece is usually held by hand and is pressed against the abrading tool, which is diflicult and only permits a comparatively low working pressure. These drawbacks are eliminated by a carrying device having the features set forth herein, particularly if this carrying device has the characteristic features in which fluid pressure means is means and the worker only has to set or adjust the position of the workpiece during the treatment.

Further features of the invention will become apparent from the following description of some preferred embodiments which are illustrated in the accompanying drawings, in which:

FIG. 1 is a side view of a belt grinding machine having a carrying device according to the invention;

FIG. 2 is a front View of this machine;

FIG. 3 is a front view on a larger scale of part of the carrying device, partly in section;

FIG. 4 is a plan view on the line 44 in FIG. 1;

FIG. 5 is a partial section on the line 55 in FIG. 4; and

FIGS. 6 and 7 illustrate a front view and a section on the line 7-'7 in FIG. 6 respectively of another embodiment of the carrying device.

The machine illustrated in FIGS. 1 and 2 comprises a base or framework for a driving roller 11, a tightening roller 12, a preferably elastic contact or supporting roller 13 and an electric drive motor 14 for an endless abrasive belt 15. In front thereof a pendulum 17-19 is suspended from a bearing block 16 in the ceiling of the room. This pendulum is constituted by a frame which comprises a beam 17, which is rotatable on a vertical axis 20, a U- shaped lower portion 18 and two parallel rods 19, which are rotatable on a horizontal axis 21 and connected with the members 17, 18 by means of upper and lower pairs of pivot pins 22 and 23 respectively, which are perpendicular to the planes of the members 17, 18. A U-shaped bracket or holder 25 for the workpiece 24 (FIG. 4), which may be the cast arm of a sewing machine, is rotatably journalled in the lower portion 18 of the pendulum, substantiall at the level of the axis of the roller 13, by means of two opposed stub shafts 26 each being associated with a hand wheel 27. The workpiece 24 can be clamped in the holder between a fixed disc 28 and an opposing disc 29, which is Patented July 21, 1970 secured to a stub shaft 30 which is non-rotatable with respect to the holder 25 but axially displaceable in one of the stub shafts 26 by means of the handle 32 of a fluid operated cylinder 31 on the adjacent rod 19 (FIG. 1). A rigid, rectangular frame 33 (FIGS. 4-5) which surrounds the abrasive belt 15 below the supporting roller 13 and has end portions 34, 35 is slidably supported in a portion 36 of the base and is displaceable by means of a fluid operated cylinder 37 (FIG. 4), which is located between said portion and the end portion 34 and is associated with a foot control 38 at the location of the grinder. A horizontal pressure roller 39 having a convex circumference is by means of ball bearings centrally journalled on the portion 35 of the frame 33 (FIG. 5) in front of a horizontal guideway or race track 40 at the bottom of the lower portion 18 of the pendulum 17-19.

When the frame 33 is in its foremost end position (to the right in FIG. 1) the holder 25 is suspended in a loading position which may be determined by the roller 39 and in which the workpiece 24 easily may be inserted and pneumatically clamped in the holder. By means of the foot control 38 the cylinder 37 may be caused to pull the frame backwards, the pendulum 1719 being pivoted clockwise by the roller 39, whereby the workpiece is pressed against the abrasive belt 15 with a hydraulic or pneumatic fluid pressure, which preferably is adjustable by means of a reduction valve (not shown) in the fluid conduit to the cylinder 37 and is substantially higher than the manual pressure which can be created by the grinder, for obtaining a high abrading ability. With one hand placed on each hand wheel 27 the worker may, at the grinding of the front, rear and upper sides of the illustrated sewing machine arm 24, easily turn the holder 25, vertically on the stub shafts 26, horizontally on the axis 20, and laterally on the pivot pins 22. Hereby, the roller 39, which is journalled in a ball bearing (FIG. 5), offers but a minor resistance against these adjustment movements when it is pressed against its guideway 40. To limit the lateral movements of the holder 24, said guideway may be provided with two abutments 41 for the roller 39 (FIG. 3). When the holder 25 is rotated vertically (on a substantially horizontal axis), which entails a substantial increase of the distance of the stub shafts 26 from the abrading belt, e.g. when continuing from treating the front or rear side of the sewing machine arm to the treating of the upper side thereof, which has a substantially greater distance from the stub shafts, it can be suitable to disconnect the pulling or pressing device comprising the members 33, 39, temporarily. After the treatment or working operation, this pressing device is returned to its foremost position by adequate manipulation of the foot control 38. Hereby, the holder 25 rotates back to its loading position, in which the workpiece 24 may be loosened by means of the handle 32 and removed.

The pressing device 33, 39 may also be driven hydraulically, or pneumatically or hydraulically in one direction and by means of a pair of tension springs, which are anchored in the members 34, 36, in the opposite direction.

The control of the driving cylinder 37 may also be so arranged, that the foot control 35 only has to be temporarily depressed for shutting the pressing means on or off. The pressure roller 39 and its guideway 40 may possibly change places. Instead of being supported by a roller 13, the abrading belt 15 may, in a manner known per se, be supported by a plate at its working place or by two relatively small supporting rollers on each side of this location.

The carrying device illustrated in FIGS. 6 and 7 comprises a single pendulum 'rod 50, 51 which is suspended in a bearing block 52 in the ceiling by means of a universal joint 53 which is rotatable on a vertical axis 63, and its lower end is rigidly connected to a circular frame 54, in which a horizontal shaft 55 having hand wheels 56 at its respective ends is rotatably journalled. To this shaft there is secured, a preferably disconnectable holder 57 for the workpiece 58, e.g. a cast lid of a wafile iron, which is clamped in the holder and which is to be polished externally. In its loading position, the holder is freely suspended in front of a rotating, stationary journalled polishing disc. The lower portion 59 of the frame 54 forms the guideway or race track of a pressure roller 60 in the pressing means 61, which may be arranged in substantially the same way as the pressing means 33, 39. The holder 57 is adjustable in substantially the same way and to the same extent as the holder 25. To be utilisable in different grinding and polishing machines, the pendulum rod may consist of two telescopically displaceable portions 50, 51 having a plurality of alternative bores in which a bolt 62 may be selectively inserted. The rod may be hingedly connected with the bearing block 52 in any other suitable manner, e.g. by means of a universal joint.

The advantages of the carrying device according to the invention and the high grinding pressure permitted thereby will get their rights if the device is utilized in combination with an abrasive belt which, according to a further aspect of the invention, comprises an endless and jointless, porous web having high tensile strength, a thin base layer of an adhesive anchored in the pores of said porous web, a surface coating, which has greater thickness than said base layer, adheres thereto, and consists of a solidified mixture of a layer of adhesive, which forms a minor constituent of said mixture, and a plurality of superimposed layers of abrasive grains which form the major constituent of said mixture and are at least partly embedded in the last mentioned adhesive.

The initial step in the manufacture of such belts is the mixing of a somewhat creamy or greasy composition of abrasive grains and an adhesive binder, which may stand some hours before being applied to the base or backing of the belt.

The abrasive of this composition may consist of any abrasive available on the market, preferably corundum, silicon carbide or natural emery having a grain size ranging between 46 and 310. The last-mentioned size may to advantage be employed for the grinding or polishing of the working surface of e.g. smoothing irons. The binder may be of the water-glass type, such as abrasive cement for polishing discs, available on the market in the form of a grease. A plastic binder, particularly a cold-setting one, as well as a skin glue, in which latter case the composition or mixture of abrasive and binder should be heated when being applied to the backing or base are suitable. The composition may contain e.g. 60 volume percent electro-corundum No. 80, and 40 percent abrasive cement, to which possibly some water has been added. The thickness of the layer of this abrasive composition when applied to the backing may be of the order of 2.0-2.5 mm.

As base or backing for the comparatively thick coating of abrasive and binder it might be possible to use a conventional web of cloth, but with high cutting rate and heavy grinding pressure jointless chromie leather belts, preferably having a thickness of the order of 4 mm. and a nylon core, are most efficient and economic. On account of their lateral stiffness they also have the advantage, that they cause essentially less chamfering at the edges of the workpiece and at possible grooves or openings therein. Leather pulley belts with a core may to advantage also be used as backings. When the surface to be treated is to be exceedingly fine, it is possible to use a woolen felt strip supported by a fabric.

New backing webs should be pre-treated by being provided with a thin base layer of an adhesive or binder, preferably of the same kind as that contained in the 4 abrasive composition. This base layer is applied by a pencil or roller and is caused to penetrate into and become anchored in the pores of the web.

The composition is applied, in any suitable manner, after that the base layer has solidified, set or cured. Thus the composition may be pressed out on the base layer by a piston through an adjustable slot in a prismatic container. Since old backing webs already have such a base layer, it is only necessary to sharpen them clean, e.g. by means of diamond powder, an edge of a hardrolled steel plate or a silicon carbide rod.

It is also possible to make abrasive belts having a proportion of abrasive greater than e.g. by subsequcntly strewing additional abrasive grains, at another location, to the previously applied but not yet completely solidified abrasive coating.

Before that said abrasive coating has been completely set or cured it is also possible to make oblique or inclined impressions therein to impart a rifled surface to said coating for increasing the cutting rate and/or reducing the heat development during the grinding operation.

When an abrasive belt according to the invention is associated with a carrying device of the kind described above in a grinding or polishing machine, in which the workpiece is pressed against the belt under a pneumatic or hydraulic pressure, the belt has, at the grinding of a larger surface of a piece of cast iron, 15 times greater life and a multiplied working speed in comparison with the leading abrasive belt manufacturers belts available on the market.

The embodiments described above are, of course, to be regarded merely as non-limiting examples and may as to their details be modified in several Ways in the scope of the appended claims.

What I claim is:

1. A device for carrying a workpiece in a grinding or polishing machine having manually controlled feed and a movable grinding or polishing tool, said device comprising: a workpiece holder having at least one handle for manually adjusting the position of said holder and the workpiece inserted therein; an elongated pendulum device which is rotatably and pivotably supported at one of its ends and is provided at its opposite end with means for rotatably carrying said workpiece holder; and pressing means for holding said holder and the workpiece against said tool, said pressing means being movable in a substantially horizontal direction, and activatable and disactivatable in dependence of said manually controlled feed and including a pressure roll for transferring pressure from said pressing means to said holder in said horizontal direction against the tool, said pressure roll permitting manual adjustment of the setting of said holder in another horizontal directionsubstantially perpendicular to said first horizontal direction during the treatment of the workpiece.

2. A carrying device according to claim 1 wherein said pendulum device is a substantially rectangular frame which is pivotable on a first axis, which substantially coincides with one of the short sides of the rectangular frame, and in addition thereto is rotatable on an axis which is substantially perpendicular to said first pivot axis.

3. A carrying device according to claim 2 wherein said pendulum device has four additional pivot axes which are each located near an individual one of the four corners of said rectangular frame, each additional axis extending in a direction which is substantially perpendicular to that of said first pivot axis as well as that of said axis of rotation to permit swinging of said workpiece holder in two mutually perpendicular directions.

4. A carrying device according to claim 3, wherein said pivot axes as well as the axis on which said workpiece holder is rotatable are substantially horizontal, and wherein said axis of rotation is substantially vertical.

5. A device for carrying the workpiece in an abrading machine having manual feed and a movable abrading or polishing tool comprising:

(a) aworkpieceholder;

(b) a support device for said workpiece holder:

(0) a displaceable means associated with said support device and cooperating therewith for displacing said support device;

(d) fluid operated means for advancing said displaceable means, said support device, and said workpiece holder towards said tool and thereby pressing said workpiece against said tool; and

(e) two-component means for transferring pressure from said displaceable means, when it is being displaced, to said support device and for enabling lateral motion of said workpiece holder in said support device during the transfer of pressure, one of the components including a pressure roll and the other component including a guideway cooperating with said roll and extending horizontally and perpendicularly to the direction of movement of said displaceable means, one of said components being carried by said workpiece holder and one of said components being carried on said displaceable means.

References Cited UNITED STATES PATENTS HAROLD D. WHITEHEAD, Primary Examiner US. Cl. X.R. 51-234, 97 

